This plant grows very well for me, except I want to point out that you need to watch the sun exposure because mine got sunburned quickly on one side until I moved it. It prefers bright light but not direct sun on the plant.

The subspecies 'spinosissima' only rarely grows higher than 12 inches. It has dirty white spines and does not have the bristles in the axils most of the time.
The subspecies 'tepoxlana' has yellow spines.
The subspecies 'pilcayensis' has whiter spines and the stems can grow to 20 inches long/high. It might have some latex/bristles in the axils.
The flowers are purple-pink on all subspecies.

This cactus can grow to over 12" tall and 4" thick. Mostly solitary but can form pups on old plants. It is very variable due to it's wide area of origin in Mexico. The color of the spines are usually red or rust (common name Red headed Irishman), but can be white. Flowers are red to deep pink in color and are about 3/4" across.